sorry to inform you that you just adjusted the purity rings,not a good thing to do-you need to get them back to the original place,you should find a paint line that lines up those rings,dont worry too much just get them back correct or your picture will never be correct.the pot you are looking for is on the main chassis,the lopti is the black plastic unit inside the metal enclosure with a thick red lead that goes to to tube,this is the ht lead there is probably 20,000 volts on this so please dont touch this lead(when i mean dont touch i refer to you unplugging it).obviously i am not aware of your experience on monitors but there are things you must never adjust,purity rings and preset voltages are two.